Gun owners really are very helpful folks for the most part, not exactly sure why, but I bet the fact that we have to stand together to keep our sport from becoming marginalized politically is part of it. There is more to it though; I remember running into an old man (late 60s) while I was still very young (19ish) at the ammo shelf of a sporting goods store and him striking up a conversation about firearms and target shooting. It was like we had known each other a long time and we ended up chatting probably a good 20-30 minutes, even though we were complete strangers 40 years apart; this hobby/sport just brings people together.
Another reason might be the inherent danger associated with the sport as well. While it can be safe if the rules are followed, it can also be very dangerous if they are not. As such, we tend to bond together for collective safety and police each other so no one gets hurt.